The past several years have been an exciting period for genome engineering. The ZFN (zinc finger nucleases), TALEN (transcription activator-like effector nucleases), and especially the more recent CRISPR (clustered regularly interspaced short palindromic repeat) technologies have profoundly increased the efficiency for precisely editing the genome of cell lines and model animals. In the past year, our unit has devoted a large portion of our efforts on developing these new technologies. We have successfully used all three methods in creating both genetically engineered mouse models and pluripotent stem cell lines. The extraordinary high efficiency of the CRISPR method has enabled us to achieve gene knockout in difficult mouse strains, such as immunocompromised mice, and target multiple genes simultaneously. Besides developing the new genome engineering technologies, we have continued to use our knowledge and technical expertise to provide a range of services in genetic engineering, animal model, and stem cell areas. These services include creating transgenic lines using the classical and the more recent site-specific (TARGATT) transgenic methods, generating knockout mouse lines using the conventional ES cell-mediated gene-targeting, mouse line cryopreservation and resurrection through in vitro fertilization, ES/iPS cell line derivation from animal species, injecting stem cells into immunocompromised mice to test teratoma formation, and genetically modifying pluripotent stem cells. In addition, we have also spent a portion of our time on exploring tissue engineering methods and creating animal models for cell transplantation. Throughout the year, we have provided numerous consultations and technical assistances to scientists with in and out of NHLBI to assist them in conducting mouse molecular genetic research, including designing DNA constructs, searching database, collecting various stages of embryos, and deriving mouse embryonic fibroblasts (MEF). I am also a member of the NHLBI Animal Care and Use Committee (ACUC) for reviewing animal protocols and conducting animal facility inspections.